Average between dates

Tomas1212 - Well, you are going to put your "customer" column in a table or matrix visualization and then create a measure that probably uses AVERAGEX at some point. 

Please first check if your issue is a common issue listed here: https://community.powerbi.com/t5/Community-Blog/Before-You-Post-Read-This/ba-p/1116882

Also, please see this post regarding How to Get Your Question Answered Quickly: https://community.powerbi.com/t5/Community-Blog/How-to-Get-Your-Question-Answered-Quickly/ba-p/38490

The most important parts are:
1. Sample data as text, use the table tool in the editing bar
2. Expected output from sample data
3. Explanation in words of how to get from 1. to 2.

I would suggest you do this with a calculated column in your order table with an expression like this

Days Since Last Order =
VAR thisdate = Orders[OrderDate]
VAR lastorderdate =
    CALCULATE (
        MAX ( Orders[OrderDate] ),
        ALLEXCEPT ( Orders, Orders[Customer] ),
        Orders[OrderDate] < thisdate
    )
RETURN
    DATEDIFF ( lastorderdate, thisdate, DAY )

Once you have that, you can simply use this as a measure to get your result

Avg Days Between Orders = AVERAGE(Orders[Days Since Last Order]) 

If this works for you, please mark it as the solution.  Kudos are appreciated too.  Please let me know if not.

Regards,

Pat